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Class D Switching Power Amplifiers and Power D/A conversion

What is wrong with TPA3255?
What is wrong with TPA3255?
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Old 20th September 2017, 01:39 AM   #151
SanjeevM is offline SanjeevM
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Join Date: Jun 2017
You're right. I am waiting for the new caps to come. Planning to build a 60000 uf bank. I will have to find a soft start circuit too.

BTW any idea how it works?
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Old 20th September 2017, 02:35 PM   #152
emedia4u is offline emedia4u  United States
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Quote:
Originally Posted by SanjeevM View Post
BTW any idea how it works?
It should be slow charge and fast discharge connected to RESET.
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Old 20th September 2017, 04:08 PM   #153
doctormord is offline doctormord  Germany
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That wont help the transformer at all.

Suitable Inrush-Current-Limiter.

PVDD: 38V
VAC: 120V
VDC_hv_virtual: VAC*1,414 ~170V
CBulk: 6000uF + 2x2200uF (EVM) ~ 10000uF
Esec = (C*PVDD^2)/2 = (0.01F * 38^2V^2)/2 = 7.22J
CBulk_hc_virt = (Esec*2)/VDC_hv_virtual^2 = (7.22J*2)/170^2V^2 = 500uF (@170Vdc)

Lets assume 600W maximum system power and 90% efficiency for the transformer.
600W/120VAC * 0.9 = 4.5A

For 3A maximum allowable input current (primary) we have:

R = VDC_hv_virtual / I = 170V/3A = 57R

Inrush current limiter needed:

R = 56R
E = 7.2J
I = 4.5A

IRC choosen: SL22 50004

Source: Inrush Current Calculators and How to Select an Inrush Current Limiter

Use in series with primary.

Last edited by doctormord; 20th September 2017 at 04:15 PM.
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Old Yesterday, 01:03 AM   #154
SanjeevM is offline SanjeevM
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Join Date: Jun 2017
I am planning to use this Soft start board::

EA - Transformer Soft Start, EATSS01 – Eight Audio(R)

The module adds resistors during startup in the AC path to limit inrush current. (That''s what the rep said!).

Last edited by SanjeevM; Yesterday at 01:06 AM.
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Old Yesterday, 10:31 AM   #155
impuls60 is offline impuls60  Norway
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Looks similar in function to what I ordered 220V 1000W Transformer Delay Power Soft Start Protection Board for Amplifier AMP | eBay. I plan to swith out the series resistors with a 60ohm power resistor. I wonder at what state of charge on the cap bank the soft start board should bybass the resistor?
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Old Yesterday, 01:14 PM   #156
SanjeevM is offline SanjeevM
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The resistors are meant to arrest the sudden inrush caused by caps with zero charge. Perhaps the switchover is just time dependent, lets say changing over after one second, which is enough to pre charge the cap bank.

I have an old Yamaha HT. On power on, the relay clicks after a second.
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Old Yesterday, 01:16 PM   #157
SanjeevM is offline SanjeevM
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Since this circuit is connected to the primary side of the trafo, it will not see the capacitor bank.
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Old Yesterday, 03:54 PM   #158
impuls60 is offline impuls60  Norway
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It's only time dependant yes, see description on mine. Some early internett calculations points me towards 7-8 seconds to fully charge 360 000uF@ 50V with less than 5A at the 230V side.. So if you could bypass at about 6s@80%charged that would be less annoying. I don't have any experince with this so any input would be great!
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